Hi, @joolzg_svep
Thanks for creating case to us.
rw61x_sb_ble_15d4_combo_a2.bin is a BLE and 802.15.4 combo firmware(not include Wi-Fi), so its size is bigger than BLE only firmware: rw61x_sb_ble_a2.bin.
rw61x_sb_wifi_a2.bin is a Wi-Fi only firmware, not a Wi-Fi + BLE + 802.15.4 combo firmware.
As you know, Wi-Fi has more features and also more complex than BLE and 802.15.4, so its firmware is bigger than BLE only firmware, and even bigger than BLE + 802.15.4 combo firmware.
If you want to use Wi-Fi + BLE +802.15.4 together, then you need to flash rw61x_sb_wifi_a2.bin (for Wi-Fi) and also rw61x_sb_ble_15d4_combo_a2.bin(for BLE + 802.15.4.) because Wi-Fi and BLE has different CPUs in RW612. There is one Wi-Fi CPU and also one BLE CPU.
You can refer to below docs for details:
Is it clear for you?
Please let me know whether have any other concerns on this case, otherwise, please do not hesitate to mark my answer as a solution so that we can close this case.
Best regards,
Christine.